Create empty Grpc files on LUT build

[eNeRGy164]

Description

Create a workaround that generates an empty file if it is a Live Unit Testing build.

Issue reference

Will close: #685

Checklist

Please make sure you've completed the relevant tasks for this PR, out of the following list:

• Code compiles correctly

[rynowak]

hi @eNeRGy164 thanks for digging into this. I've pinged the .NET gRPC maintainer to see if I can understand this better. Please sit tight a bit while I do research.

[halspang]

@eNeRGy164 - This fell off of our radar, but is it still something you'd like to see? I can see if any progress was made originally/if I can follow-up myself.

[WhitWaldo]

@eNeRGy164 Thank you for your contribution!

I'm going to close this PR as we haven't heard anything from you in the last year and with v1.15, the shape of the solution is changing a bit. The various Dapr.* projects do not implement from the protos directly and instead reference them from Dapr.Protos, so creating the empty prototype here for testing no longer feels quite relevant. That said, if a the scenario comes up in which we wind up needing to add this to the Dapr.Protos file, I'll make sure you assign you for attribution on the PR.